Prologue – A part at the beginning of a play/story that introduces it and establishes the background
They protested against the logging (prologue). It was a good job they got there at the beginning. The speaker stood on the logging machine and established the background to what this machine was about to do.
Examples of prologue in a sentence
She got to the cinema late and missed the film's prologue, which left her completely clueless about the story.
The book's prologue actually focused on the antagonist, but this wasn't revealed till later in the story.
The prologue was far too long and didn't really add anything to the play's story.